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Exam papers

Exam papers. Jan13 pomegranates/arsenic ..G628 Exam papers2013 Jan142432-mark-scheme-unit-g628-sampling-testing-and-processing-january.pdf Jun 11 apples/mercury ..G628 Exam papers2011 June62209-question-paper-unit-g628-sampling-testing-and-processing.pdf

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Exam papers

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  1. Exam papers • Jan13 pomegranates/arsenic • ..\G628 Exam papers\2013 Jan\142432-mark-scheme-unit-g628-sampling-testing-and-processing-january.pdf • Jun 11 apples/mercury • ..\G628 Exam papers\2011 June\62209-question-paper-unit-g628-sampling-testing-and-processing.pdf • ..\G628 Exam papers\2011 June\64018-question-paper-unit-g628-sampling-testing-and-processing-insert.pdf • http://www.ocr.org.uk/Images/63955-mark-scheme-unit-g628-sampling-testing-and-processing-june.pdf

  2. G628 Sampling, testing and processing DATE: 21st March 2014 Title: Identification, obtaining and storage of samples LO:to understand the analysis of substances Lesson outcomes: All D= Most C = Some B = Starter- get out exam paper Jan 13, ready to mark

  3. The chemical industry is not just about the making and selling of chemicals. It is equally about the analysis of chemicals from a variety of different sources. The analytical sector is a vast industry employing many scientists and technicians covering the public, academic and private sectors. It is estimated that as a whole it has an annual turnover in the UK of about £7 billion pounds. Analysts are asked to identify and quantitate (find out how much) substances in samples from a wide variety of sources.

  4. Analysing substances for a purpose: • Analyses falls into 2 main categories: • Quantitative – is about determining the amount(s) present in the sample • Qualitative – is about identifying if something is present in the sample

  5. Obtaining a sample for analysis: • When you take a sample of a substance for analysis the sampling method you used depends on : • source and nature of the substance • and what you want to know about the substance • One very important factor that always should be considered is: • Is the sample you are taking representative of the source you are taking it from? Is the distribution of the substance uniform?

  6. If you are unsure that the substance is uniformly distributed you need to take samples from different places. This is called random sampling. If the sample is uniformly distributed throughout (homogeneous) then a single sample can be used. This does tend to be the case for most pure substances and mixtures. If the composition of a mixture varies (heterogeneous) you all ways need to take a number of representative samples.

  7. When samples are to be collected a number of requirements need to be considered • What is the purpose of the collection? • Is the source of the material homogenous or does its composition vary? • Are samples affected by storage and if so how long can they be kept before they need to be tested? • Should more than one sample be collected for testing and where from • In collecting samples, what are the possible dangers involved? (weather changes or environmental hazards, or sample itself) • Once sample has been collected, which method of testing should be used to obtain the best results • Is any modification of method required?

  8. Identification of the requirements • decide where, when and how often to take samples - example could use would be glucose tolerance test. • How many samples to take – Glucose Tolerance Test is a good example. • Collect samples with regard to any possible hazards and to assess any risks present. • Health and safety implications of their sampling. • Most appropriate size of the sample to take - GTT is good example. • Most appropriate way of storage of sample before testing. • Know what to do if their sampling method does not work i.e. adapt and modify or use alternative.

  9. Obtaining representative samples and storage p169 • Use an appropriate sampling method to obtain a representative sample. • Be certain that the correct conditions for sampling are observed. • Prepare and use the correct equipment for sampling – e.g. the correct size of pipette to measure out a volume of liquid to ensure accuracy. • Control the conditions when collecting so that samples are of optimum quality • Storage under correct conditions. • Record details of samples selected - (when - date /time, where, from whom etc) • Clean sample equipment and disposal of material - H and S. Good examples from blood collection. • Ensure safe operating procedures are followed - H and S.

  10. Testing P170-172 • The properties to be determined • Select, adapt or devise a suitable method for testing. • Know how to prepare the testing equipment for use. • Ensure that they are aware of any potential hazards that may occur during testing - H and S. • Follow the testing method in the correct order, modifying as necessary – must follow a set of written instructions!! • Record any modifications to the normal testing method. • Accurately record the results of a test – do not record to 10 significant places and do not forget the units!! • Know how to clean the testing equipment and dispose of materials correctly

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